The present invention relates to the structure of a small flat brushless motor and its assembly method.
Portable information equipment (hereafter referred to as xe2x80x9cequipmentxe2x80x9d) including, for example, cellular telephones are desired to be smaller, lighter, and thinner, to give a sophisticated impression, and to endure longtime use. Equipment manufacturers are making various efforts to meet these demands. They are attempting to reduce the size and power consumption of electronic parts integrated into the equipment, to use multilayer wiring substrates to allow electronic parts to be densely integrated while increasing productivity, and to configure enclosures using light metal such as magnesium to reduce the thickness of the equipment and give it a sophisticated impression. There are similar demands on flat brushless motors used as a drive source for the equipment.
A vibration generating function for silent calls is now essential for cellular telephones. The vibration generating function is generally implemented by a vibrating motor with an eccentric weight. This is because such a motor has excellent characteristics such as a small size, a low power consumption, and a low price and is thus advantageous in reducing the weight of the equipment. The vibrating motor must also serve to improve the value of the equipment.
Requirements on vibrating motors and flat brushless motors used as equipment drive sources (hereafter, these motors may be collectively and simply referred to as xe2x80x9cbrushless motorxe2x80x9d or xe2x80x9cmotorsxe2x80x9d) that should to be met to improve the value of the equipment will be considered. First, brushless motors must be adapted for the improved degree of integration of the equipment. Thus, as in other solid electronic parts, the brushless motor can desirably be mounted on a substrate of the equipment using xe2x80x9csurface mount technology.xe2x80x9d This is because in case of a multilayer substrate, the degree of integration may decrease if terminals are passed through holes formed in the substrate. In order to improve the degree of integration, the brushless motor is desirably configured by being mounted close to adjacent electronic parts so as to achieve a high density.
Second, the brushless motor must be adapted for the same mounting process as other solid electronic parts in order to increase the productivity of the equipment. Thus, the brushless motor desirably has a configuration and a heat resistance compatible with a reflow soldering method. It is also desirably configured by being efficiently mounted using the same assembly machine as other solid electronic parts.
Third, the brushless motor must be adapted for the reduced size and weight of the enclosure of the equipment. Thus, it desirably has a high impact resistance.
The reasons for the demand for the high impact resistance will be described. Of course, the high impact resistance is required to ensure that the equipment will not be destroyed even if it is inadvertently dropped. Conventional common methods provide a certain amount of space inside the equipment and integrate the motor into the equipment via an elastic body. In recent years, however, the demand for reduced size and thickness prevents a space for the elastic body from being provided. If an attempt is made to surface-mount the motor on the same substrate as other electronic parts in order to meet the demand, the brushless motor is directly fixed to the substrate, thereby preventing impacts to be absorbed as in elastic support structures.
Furthermore, attempts are being made to form the enclosure of the equipment of light metal such as magnesium or aluminum, as described above. Despite its small weight, such metal has a much higher rigidity than resin so its buffering capability is insufficient. Consequently, an unprecedentedly large impact is effected on the substrate fixed to the enclosure and is directly transmitted to the motor fixed to the substrate. As a result, a very high impact resistance is required of the motor and its coupling. Therefore, the desired value of motor impact resistance is conventionally between 3,000 and 5,000 G but now between 10,000 and 20,000 G.
Besides, this impact resistance is desirably met by simply heating and melting a solder on the substrate to solder-connect the motor to the substrate (reflow) without passing terminals through holes formed in the substrate (surface mount). Even enduring a reflow heating temperature (about 250xc2x0 C.) is difficult. The inventor attempted to find a conventional technique that meets these requirements, but in vain. Thus, through many examinations, the inventor has completed the present invention. A motor according to the present invention is of a flat type having a height smaller than the breadth, so it is sometimes referred to as a xe2x80x9cflat vibrating motorxe2x80x9d or a xe2x80x9cflat brushless motor.xe2x80x9d
Next, brushless motors will be described by focusing on conventional assembly methods.
A small flat brushless motor generally comprises a metal base on which various parts are assembled. Since the motor is a rotational power source for the equipment, it must be mounted in the equipment so as to maintain a sufficient rigidity and the metal base must be formed accurately so as to be suitable as a criterion for motor assembly. To assemble the motor, the base is placed on a palette (a positioning working table) and the parts are then mounted on the base.
According to this assembly method, before placing the base on the palette, whether or not the base is located upside down is checked and its direction and position are adjusted. The time required for this operation, however, tends to increase with decreasing size of the motor. This is because it is more difficult to handle smaller parts. This tendency is found not only in the positioning of the motor base but also in the assembly of electronic parts on a printed circuit board. The electronic parts are difficult to efficiently mount on a small printed circuit board.
In addition to the reduced size, there is a strong demand for the reduced weight of the motor for portable equipment. However, in attempting to reduce the size and weight of the motor, the characteristics of the motor must not be sacrificed. Thus, a rotor and a stator must naturally have a specified size and weight. Accordingly, it is now necessary to reduce the volume and weight of peripheral members including structures other than the rotor and stator, that is, a structure for holding the rotor and stator and a structure for electrically connecting the stator and external device together.
The printed circuit board assembly method called the xe2x80x9cconnected substratexe2x80x9d is conventionally commonly used to produce built-in circuits for various equipment. When printed circuit boards have small or different external shapes, this method arranges a large number of such circuit boards and connects them together using bridges or frames so as to form a shape that is easily handled by an electronic parts mounting machine. After electronic parts have been mounted on these circuit boards, the bridges are cut and removed to obtain printed circuit board assemblies in order to complete assembly.
This method, however, is still disadvantageous if further size reduction is required. In addition, as the size of the printed circuit board decreases, the area occupied by the bridges or frames relatively increases to reduce the usage of material resources. In addition, despite a demand for further reduction of the size of the printed circuit board, when a shearing machine is used to cut the bridges, contacts with the cutting edge and stress caused by shearing must be avoided. As a result, no part can be placed near the sheared position. The bridges may be folded or ruptured, but the separated portion form a rough rupture surface to degrade the appearance and dimensional accuracy. Due to these disadvantages, this method is unsuitable for small parts. Furthermore, since the separation is carried out after the completion of assembly, an impact associated with shearing may degrade the quality of finished products.
Thus, an assembly method is desired that solves these problems in configuring a compact motor by mounting parts on a printed circuit board densely.
In attempting to meet these demands, another object is to reduce the volume and weight of the members such as the structure for holding the rotor and stator and the structure for electrically connecting the stator and external device together.
A first object of the present invention is to meet the above requirements, that is, to contribute to improving the degree of integration of the equipment. Thus, the motor must be configured by being mounted on the substrate of the equipment using the SMT technology and to be mounted close to adjacent electronic parts so as to achieve a high density.
A second object is to contribute to improving the productivity of the equipment. Thus, the motor must have a configuration and a heat resistance compatible to the reflow soldering method and must be configured by being efficiently mounted using the same assembly machine.
A third object is to contribute to reducing the size and weight of the equipment. Thus, the motor must have a sufficient impact resistance.
A fourth object is to improve the assembly productivity. Thus, the present invention must provide a structure that is easier to handle and assemble and an assembly method for such a structure.
A total object of the present invention is to attain the above objects to provide portable information equipment having a reduced size and weight, an increased productivity, and high added values.
In order to attain these objects, a brushless motor according to the present invention comprises a housing comprising a bottom surface, a side surface, and a top surface, the bottom surface being located adjacent and opposite to a substrate of an equipment; pairs of terminals on the bottom surface that can be mechanically or electrically joined with the substrate of the equipment; a stator, a bearing device, and a rotor inside the housing, the stator having a stator core and a coil wound around it, the rotor having a magnet and supported by the bearing device so as to rotatably surround the periphery of the stator, the rotor further including unbalance means or housing drive means that protrudes from part of the housing and that rotates with the rotor.
In addition, in order to solve the problems with the assembly of the brushless motor, a motor assembly method according to the present invention uses a motor base connector. The motor base connector comprises motor bases each using a plate-like material as a base material and comprises a plurality of motor bases and a skeleton that remains after these motor bases have been punched out, the plurality of motor bases being pushed back and held in the skeleton. Each motor base is completed by executing the steps of fixing the bearing device and the stator to a stator mounting surface, assembling the rotor on the bearing device, and removing the motor from the skeleton.
Next, the structure of the brushless motor and its assembly method according to the present invention are described in detail.
First, a flat brushless motor according to a first aspect of the present invention is adapted to meet the following requirements:
(a) The motor has a housing comprising a bottom surface, a side surface, and a top surface.
(b) The bottom surface is located adjacent and opposite to a substrate of an equipment. The motor has on this bottom surface, pairs of terminals that can be mechanically or electrically joined with the substrate of the equipment. The pairs of terminals are arranged on both sides around a line passing through the centroid or center of gravity of the bottom surface.
(c) The motor comprises a stator, a bearing device, and a rotor, all inside the housing. The stator has a stator core and a coil wound around the stator core. The rotor has a magnet and is supported by the bearing device so as to rotatably surround the periphery of the stator.
(d) The rotor further includes unbalance means.
With these terminals, the motor can be joined with the substrate of the equipment by reflow soldering method (solder joint). The housing facilitates handling of the motor. When prevented from protruding from the bottom surface area outward sideways, the terminals on the bottom surface can be arranged close to adjacent electronic parts. In addition, through the terminals may further protrude perpendicularly from the bottom surface so as to engage with holes in the substrates of the equipment, such an embodiment that the terminals are surface-connected to the substrate of the equipment is essentially desirable for the equipment.
In addition, since the terminals are arranged so as not to concentrate in part of the bottom surface, they can cooperate in efficiently bearing an impact, thereby providing a large holding force. Desirably, the impact can be more evenly shared by arranging the terminals point-, line-, or rotation-symmetrically around the centroid or center of gravity of the bottom surface.
According to more detailed explanation, the expression xe2x80x9ccenter of gravityxe2x80x9d may be paraphrased as a point where the center of gravity on the whole is vertically projected on the bottom surface. Furthermore, the centroid means the center of gravity on a plane figure.
A flat brushless motor according to a second embodiment of the present invention is adapted to meet the following requirements:
(a) The motor has a housing comprising a bottom surface, a side surface, and a top surface.
(b) The bottom surface is located adjacent and opposite to a substrate of an equipment. The motor has on this bottom surface, pairs of terminals that can be mechanically or electrically joined with the substrate of the equipment. The pairs of terminals are arranged on both sides around a line passing through the centroid or the center of gravity of the bottom surface.
(c) The motor comprises a stator, bearing device, and a rotor, all inside the housing. The stator has a stator core and a coil wound around the stator core. The rotor has a magnet and is supported by the bearing device so as to rotatably surround the periphery of the stator.
(d) External drive means that rotate with the rotor protrudes from part of the housing.
Preferably, the external drive means protruding from the housing is, for example, a shaft, a gear, a pulley, or part of the rotor. It reasonably protrudes from the top surface but may protrude from the bottom surface or part of the side surface depending on the requirements on the equipment.
A flat brushless motor according to a third embodiment of the present invention is adapted to meet the following requirements:
(a) The motor has a housing comprising a bottom surface, a side, and a top surface.
(b) The bottom surface is located adjacent and opposite to a substrate of equipment. The motor has on the side of the housing, pairs of terminals that protrude from the side approximately at the same height as the bottom surface and that can be mechanically or electrically joined with the substrate of the equipment. The pairs of terminals are arranged on both sides around a line passing through the centroid or center of gravity of the bottom surface.
(c) The motor comprises a stator, a bearing device, and a rotor, all inside the housing. The stator has a stator core and a coil wound around it. The rotor has a magnet and is supported by the bearing device so as to rotatably surround the periphery of the stator.
(d) The rotor further comprises unbalance means.
In this manner, the terminals protrude from the side of the housing, so these terminals can be provided in addition to the terminals within the bottom surface area to further increase the number of terminals, thereby increasing fixing strength. This configuration may also correspond to the reflow method that locally heats the protruding terminals.
A flat brushless motor according to a fourth embodiment of the present invention is adapted to meet the following requirements:
(a) The motor has a housing comprising a bottom surface, a side, and a top surface.
(b) The bottom surface is located adjacent and opposite to a substrate of equipment. The motor has on the side of the housing, pairs of terminals that protrude from the side approximately at the same height as the bottom surface and that can be mechanically or electrically joined with the substrate of the equipment. The pairs of terminals are arranged on both sides around a line passing through the centroid or center of gravity of the bottom surface.
(c) The motor comprises a stator, a bearing device, and a rotor, all inside the housing. The stator has a stator core and a coil wound around the stator core. The rotor has a magnet and is supported by the bearing device so as to rotatably surround the periphery of the stator.
(d) External drive means that rotate with the rotor further protrudes from part of the housing.
In this manner, the terminals protrude sideways of the housing, as in the motor according to the third embodiment, so these terminals can be provided in addition to the terminals within the bottom surface area to further increase the number of terminals, thereby increasing fixing strength. This configuration may also correspond to the reflow method that locally heats the protruding terminals.
A flat brushless motor according to a fifth embodiment of the present invention is adapted to meet the following requirements:
(a) The motor has a housing comprising a bottom surface, a side surface, and a top surface and further comprising a chuck section.
(b) The bottom surface is located adjacent and opposite to a substrate of equipment. The motor has on the bottom surface or side of the housing, pairs of terminals that can be mechanically or electrically joined with the substrate of the equipment. The pairs of terminals are arranged on both sides around a line passing through the centroid or center of gravity of the bottom surface.
(c) The motor comprises a stator, a bearing device, and a rotor, all inside the housing. The stator has a stator core and a coil wound around it. The rotor has a magnet and is supported by the bearing device so as to rotatably surround the periphery of the stator.
(d) The rotor further comprises unbalance means.
This housing enables the motor to be transferred by using a loading chuck of an automatic electronic parts assembly machine and then to be automatically loaded on and soldered to the substrate of the equipment. The chuck section desirably accommodates a suction chuck, a grip chuck, and a magnet chuck, as shown below.
A flat brushless motor according to a sixth embodiment of the present invention is adapted to meet the following requirements:
(a) The motor has a housing comprising a bottom surface, a side surface, and a top surface and further comprising a chuck section.
(b) The bottom surface is located adjacent and opposite to a substrate of equipment. The motor has on the bottom surface or side of the housing, pairs of terminals that can be mechanically or electrically joined with the substrate of the equipment. The pairs of terminals are arranged on both sides around a line passing through the centroid or center of gravity of the bottom surface.
(c) The motor comprises a stator, a bearing device, and a rotor, all inside the housing. The stator has a stator core and a coil wound around the stator core. The rotor has a magnet and is supported by the bearing device so as to rotatably surround the periphery of the stator.
(d) External drive means that rotate with the rotor further protrudes from part of the housing.
As in the motor according to the fifth embodiment, this housing enables the motor to be transferred by using a loading chuck of an automatic electronic parts assembly machine and then to be automatically loaded on and soldered to the substrate of the equipment. The chuck section desirably corresponds to a suction chuck, a grip chuck, and a magnet chuck, as shown below.
In addition, according to the flat brushless motor of the present invention, the chuck section comprises a sucked surface that is located on the top surface and to which a suction chuck can be opposed. This sucked surface enables the motor to corresponds to suction chucks most commonly used in electronic parts assembly machines. The size of the sucked surface on the top surface conforms to many automatic assembly machines if the surface is flat and has a diameter of at least 3 mm or more and desirably 4 mm or more. The sucked surface may be shaped like a ring. Both an inclined surface and a spherical surface can be chucked.
In addition, according to the brushless motor of the present invention, the chuck section comprises two parallel planes located on the side and extending approximately perpendicularly to the bottom surface or two parallel ridges located on the side and extending parallel with the bottom surface. This configuration enables the electronic parts assembly machine to easily grip, load, and align the motor and also enables alignment to be checked easily. Alignment can also be carried out by using a grip chuck to clamp the two parallel ridges extending parallel with the bottom surface. If the motor appears like an n-gon as seen from the top surface ((n) is an even number larger than or equal to four), the shape of the motor is similar to a circle and thus serves to save space, while it allows the motor to be gripped by the chuck. If the motor appears like an oval or a similar shape as seen from the top surface, this shape contributes to further enlarging the internal space and is preferable in housing inside other electronic parts such as a drive circuit. If the motor appears like two parallel lines located adjacent to the outer circumference of a circle as seen from the top surface, the shape of the motor is very similar to a circle and thus serves to save space, while it allows the motor to be gripped by the chuck. If the motor appears like a combination of a base having two parallel planes and a cylinder, a cover shaped like a cylindrical cup can be easily produced to reduce costs. If an arch-shaped cover is mounted on the base in such a way as to surround the outside of the rotor, then despite the lack of protection for the inside of the motor, the arch-shaped cover contributes to saving resources to reduce costs.
In addition, the chuck section of the brushless motor of the present invention comprises a ferromagnetic member forming the top surface. This ferromagnetic member on the top surface enables the motor to be transferred by an automatic assembly machine using a magnet chuck. The ferromagnetic member is preferably a plated copper plate or a magnetic stainless steel plate.
In addition, the brushless motor of the present invention further has on the top surface or side, a marking for enabling the mounting direction of the motor to be determined. With this marking for enabling the mounting direction of the motor to be determined, the motor can be loaded in the correct direction by using an automatic assembly machine. The marking may exhibit a reflectance or magnetic reaction different from that of the periphery or may protrude or be recessed relative to the periphery. The method is selected depending on the structure and size of the motor and the configuration of an equipment assembly facility.
In addition, according to the brushless motor of the present invention, the number of terminals on the bottom surface is larger than the number of poles required for electric connections. Thus, the bottom surface has the large number of terminals including those required for electric connections, thereby increasing the strength with which the motor is mounted on the substrate to improve the impact resistance. In any of the motors, the basic concept is that the terminal has a high mechanical junction function for supporting a required weight, but separate holding means may be added that comprises an elastic body placed between the top surface and the enclosure of the equipment. The terminal may be formed of a land, a plate, a wire, or a headed pin. The bottom surface need not be the overall bottom surface but may be substantially formed of the bottom-side end surfaces of the side walls. In addition, although a configuration in which an output shaft for obtaining an output does not protrude to the exterior is preferable in protecting the interior, the rotor may partly protrude as required.
In addition, according to the flat brushless motor of the present invention, the top surface and side of the housing approximately surround the overall circumference of the rotor. In this manner, the outer rotor is further covered by the housing so as to be shielded, so the inside can be protected from the entry of hot blasts or dusts. Thus, this motor is suitable for the reflow method.
In addition, a tape-like package according to the present invention has a plurality of embosses arranged in series and in which the flat brushless motor is accommodated. Thus, the motor is supplied from the tape-like package, it can be efficiently mounted on the substrate of the equipment like electronic parts, using an automatic assembly machine.
In addition, a portable information equipment according to the present invention comprises the flat brushless motor of the present invention. Accordingly, the motor having the above characteristics can be reliably mounted so as to provide a high productivity, thereby increasing the value of the equipment.
In addition, the flat brushless motor of the present invention has a positioning member protruding from the bottom surface. Since the bottom surface has the positioning member for positioning relative to the relevant equipment, the external drive means can be accurately mounted. The positioning member is reasonably formed coaxially with the bearing device.
Next, a motor base connector according to the present invention is adapted to meet the following requirements:
(a) The motor base connector comprises motor bases each using a plate-like material as a base material.
(b) The motor base connector comprises a plurality of motor bases and a skeleton that remains after these motor bases have been punched out.
(c) The plurality of motor bases are pushed back and held in the skeleton.
Pores for positioning the skeleton are preferably provided in the skeleton. These structures allow the motor bases to be held by the skeleton, so this motor base connector is suitable for automatic assembly. In addition, by providing slit near the motor base in the skeleton, stress in the skeleton caused by the push-back is reduced to alleviate warp and deformation.
The motor base is a plate having a bottom surface, a stator mounting surface opposed to the bottom surface, and an outer circumferential side, the stator mounting surface having the stator fixed thereto. The motor base is desirably a printed circuit board, a ceramic substrate, or a metal substrate comprising a plate-like insulating material as a base material. In particular, double-side printed circuit boards are most preferable because they serve to reduce the size and weight of the motor.
In addition, a brushless motor assembly method according to the present invention is adapted to meet the following requirements:
(a) The motor base connector, the stator, the bearing device, and the rotor are used.
(b) Each motor base has a stator mounting surface and a bottom surface. The method comprises the steps of fixing the bearing device and the stator to the stator mounting surface, assembling the rotor on the bearing device, and removing the motor from the skeleton.
In this manner, the motor base can be handled as a connector, so the position and direction of the motor base can be regulated very accurately and a high-quality motor can be promptly assembled using a parts mounting machine. In addition, since no shearing operation is used to remove the motor from the skeleton, there is no possibility of quality degradation caused by an impact associated with shearing.
The method may include the steps of heating and hardening an adhesive for all the motors, carrying out batch reflow soldering, installing a cover, or conducting inspections, or as required. In addition, the motor may have either a cored outer rotor structure or a planar opposed core-less structure, but in the planar opposed core-less type, the motor can act as a magnetic path if the motor base comprises an iron substrate.
In addition, a brushless motor according to a seventh embodiment of the present invention is adapted to meet the following requirements:
(a) The motor comprises a stator, a base, a bearing device, and a rotor.
(b) The stator has a stator core and a coil wound around the stator coil.
(c) The base is a plate-like substrate comprising an electric insulating material as a base material and having a bottom surface, a stator mounting surface opposed to the bottom surface, and an outer circumferential side. At least part of the outer circumferential side or two or more portions thereof are exposed so as to be held by a skeleton. The bearing device and the stator are fixed coaxially to the stator mounting surface. Pairs of terminals are arranged on the bottom surface or the stator mounting surface.
(d) The rotor has a rotor yoke and a magnet fixed to the rotor yoke. The rotor yoke surrounds the periphery of the stator and is rotatably supported by the bearing device.
The base is desirably a resin substrate or a printed circuit board. With this base, the external size of the motor can be made as small as the diameter of the rotor by attaching the terminals to the bottom surface and the stator side and electrically connecting the terminals together through the plate material. The terminal may be formed of a land, a plate, a wire, or a headed pin. In addition, since at least part of the outer circumferential side or two or more portions thereof are exposed so as to be held by the skeleton, a reasonable assembly method can be provided in which the motor base is transferred as a connector.
Furthermore, in the brushless motor according to the present invention, the base is a double-side printed circuit board, and a plurality of lands are provided on each of the bottom surface and the stator side. This base comprising a double-side printed circuit board provides a heat resistance for soldering in motor assembly, a mechanical strength for holding the motor, and a compatibility with a method for transferring the motor by holding its outer circumferential side. By connecting the mutually corresponding lands together via through-holes, electric connections can be established while providing a light and compact motor. In addition, by providing through-holes in an outer circumference punching section, the cover can be inserted into the through-holes and fixed at the outer circumferential end of the motor base. This configuration is preferable in providing a cover having approximately the same size as the motor base.
Moreover, the portable information equipment according to the invention comprises a brushless motor which is surface-mounted on the substrate of the equipment. Thus, without providing fixing holes or the like in the substrate of the equipment, the motor can be firmly mounted with high efficiency and high density, thereby realizing miniaturization of the equipment and improvement of the productivity.
Further, the portable information equipment according to the invention includes a larger number of lands adapted for fixation of the motor of the equipment than the number of poles necessary for electrical connection of the brushless motor. As a result, the motor can be retained in a wide area and at a large number of positions, which improves the impact resistance of the equipment.
Still further, the portable information equipment according to the invention is configured such that the cover of the brushless motor is electrically grounded to the substrate of the equipment, whereby electromagnetic noise caused by the motor drive current can be shielded by the cover and the radiation noise be reduced.
Still further, the motor to be incorporated in the portable information equipment according to the invention is accommodated in a tape-like package to be supplied, and is then surface-mounted on the substrate of the equipment. Therefore, the motor can be incorporated in the equipment in a typical electronic parts assembly production line, leading to improvement of the productivity.